Biomedical Engineering Reference
In-Depth Information
Table 5.1
Composition of simulated synovial fluid.
Solvent
Additive
Concentration
(g dl
−
1
)
01 mol l
−
1
phosphate-
buffered saline
0
.
Albumin (human serum protein)
2.0
γ
-Globulin (human serum protein)
1.0
Phospholipid
-DPPC
(dipalmitoylphosphatidylcholine)
l
α
0.2
Cholesterol
0.1
Sodium azide
0.3
Adapted from Nakanishi and Higaki [1].
The boundary lubricating properties of proteins and phospholipids are changed
by the length of exposure time and contact pressure. Thus, experimental results
should be analyzed with these factors in mind. Research on how the exposure time
affects boundary film formation on bearing surfaces shows that the specific wear
rate of a polyethylene pin sliding on a metallic plate is increased by a decrease
in the exposure time, even if the contact pressure and the sliding speed are held
constant (Figure 5.7) [22, 23]. Wear joint simulation test conducted using bovine
serum lubrication showed that the dependence of friction on contact stress for
the polyethylene socket was similar to that of semicrystalline polymers under dry
10
−
7
×
8.0
6.0
4.0
2.0
0
0
1.0
2.0
3.0
Exposure time (s)
Figure 5.7
Influence of exposure time on wear of
UHMWPE. Adapted from Nakanishi
et al
. [23].
